U.S. Pat. No. 4,156,187 discloses a remote control system for controlling devices. The system utilizes a first foot-actuated transmitter that transmits signals having one of three frequencies at a time that is received by a receiver for controlling one of three devices. A disadvantage with this system, however, is that when a second foot-actuated transmitter in another room transmits a signal having one of the three frequencies, the second foot-actuated transmitter could interfere with operation of the device. Further, the second foot-actuated transmitter could inadvertently control operation of the device when no operator is present in the room having the device.
The inventors herein have recognized a need for a system for controlling devices using first, second, and third wireless radio-frequency (RF) modules, where the third wireless RF module only responds to an RF signal having first and second identifiers associated with the first and second modules, respectively, for controlling the devices. As a result, inadvertent activation of the devices by extraneous RF signals is prevented.